Managing Interfacial Hot‐Carrier Cooling and Extraction Kinetics for Inverted Ma‐Free Perovskite Solar Cells Over 23% Efficiency via Dion–Jacobson 2D Capping Layer

Abstract

While quasi‐2D perovskite is often used in inverted perovskite solar cells (PSCs) to improve the interfacial carrier transfer, the development of pure 2D perovskite with superior stability is rarely seen and the corresponding carrier‐extraction kinetics remains unclear. Here, a variety of hexatomic ring cations including piperidine, pyridine, and cyclohexane are introduced to modify the perovskite/electron transport layer interface. The Dion–Jacobson phase 2D cladding (n = 1) based on 3‐(aminomethyl) piperidinium is proved to form a coordinated energy landscape and homogeneous surface potential distribution, and effectively prolong the electron diffusion length (≈1.58 µm) and accelerate the hot‐carrier extraction rate (2.5 times that of Control at 400 K). Furthermore, the quasi‐2D treatment (n ≈ 3,4) demonstrated a slight escalation in short‐circuit current, but failed to inhibit the interdiffusion of Ag, Pb, and I under illumination. Finally, one of the state‐of‐art power conversion efficiency (PCE) for MA‐free inverted PSCs is achieved at 23.62% with increased open‐circuit voltage (≈1.15 V) and fill factor (≈82.8%). Most importantly, 89% and 93.6% of initial PCE are retained after 720 h under 85 °C heating and 1000 h under maximum power point tracking, illustrating satisfactory thermal and operational stability with pure 2D perovskite capping layer.

In situ dipole formation to achieve high open-circuit voltage in inverted perovskite solar cells via fluorinated pseudohalide engineering

“…As previously reported by our group, 3AMP is a good passivating agent used to modify the perovskite/ETL interface. 12 The result shows that the VBM of Control + 3AMP decreases by only 0.02 eV relative to Control, which is a negligible change, suggesting that 3AMP treatment alone cannot play a role in band bending. However, w/EMIMTFSI + 3AMP decreases by 0.09 eV, further bringing the CBM of the perovskite film (À3.91 eV) into line with PCBM (À4.00 eV).…”

“…This indicates the smoothest perovskite surface and the lowest degree of energetic disorder of w/EMIMTFSI, which prevents the formation of deep-level defects and promotes efficient charge transport. 3,12,47…”

“…This indicates the smoothest perovskite surface and the lowest degree of energetic disorder of w/EMIMTFSI, which prevents the formation of deep-level defects and promotes efficient charge transport. 3,12,47 To study the recombination and extraction characteristics of charge carriers, their transport behavior in perovskite films was explored by the fluorescence technique. The ultraviolet-visible (UV-vis) absorption spectra of the perovskite films are shown in Fig.…”

“…Many methods have been developed, such as the placement of dipoles at the interface, 10 passivation of Lewis acid–base molecules, 11 treatment with organometallic compounds, 3 and low-dimensional perovskite engineering. 12,13 Among them, the formation of 2D/3D heterojunctions at the perovskite/ETL interface by introducing large-volume organic molecules is one of the most popular techniques. Azmi et al use oleylammonium iodide (OLAI) molecules to form a 2D perovskite layer and adjust the dimensions of the 2D perovskite by adjusting the annealing conditions.…”

Rationally designed hole transporting layer system for efficient and stable perovskite solar cells

“…(7) The management of interfacial hot-carrier cooling and extraction toward the HTL could be the next research area in order to further improve device performance. 117,118 Effective energyselective connections must be created between the perovskite surface and the HTL in order to achieve this.…”